Current methodologies for the detection and analysis of G- and V-type chemical warfare agents (CWA) containing phosphonate esters and their products are inadequate. G-type CWA's include GB, GD and GF, and V-type CWA's include VX and Russian VX. Examples of typical neurotoxic chemical warfare agents are depicted by the following formula I: where A is an alkyl group in both G- and V-type compounds, X is fluorine in GB, GD and GF, and X is a mercaptan group in V-type agents. The existing techniques for identification of chemical warfare organophosphorus compounds (OP) rely on multi-faceted analytical data integration, and are further complicated because of the lack of adequate generic analytical methods for these compounds. They fail to rapidly detect and identify known G- and V-agents, not to mention the detection and analysis of unknown agents. The information gathered from them is inferential, time consuming, non-generic, needs expensive and extensive instrumentation, and is ineffective for the analysis and identification of unknown agents. Even known agents require confirmatory multi-instrumental analysis for reliable identification. This involves larger sample quantities and extensive effort. Further, G- and V-type agents differ in their stability characteristics, but in aqueous environments, undergo a slow spontaneous hydrolysis producing very stable methylphosphonate esters as the major phospho-products. These esters were reportedly the major metabolites after GB exposure in humans (see reference 12, listed below) and GB, GD, and GF exposure in rats (see reference 13). Because of the labile nature of these chemical warfare neurotoxins, rapid detection and analysis methodology is also needed for phosphonate ester degradation products, which are important biomarkers.
One current method, the cholinesterase inhibition assay (ChE), could indicate the presence of a chemical warfare agent containing organophosphorus compounds. However, the ChE assays are non-specific (detecting both OP and carbamates) and are subject to interferences from heavy metals. Therefore, these assays cannot even provide the information as to whether the inhibition was due to carbamates or OP, not to mention the capability to ascertain the presence of CW OP neurotoxins.
The most important nerve agents to which the process of this invention can be applied are those containing organophosphorus compounds such as, for instance isopropyl methylphosphonofluoridate (GB), pinacolyl methylphosphonofluoridate (GD), cyclohexyl methylphosphonofluoridate (GF), O-ethyl S-(2-diisopropylamino)ethyl methylphosphonothiolate (VX), and O-isobutyl S-(2-diethyl-aminoethyl) methylphosphonothioate (Russian VX or R-VX). Note that the designations GB, GD, GF, VX, and Russian VX refer to standard U.S. government designations for the respective chemical warfare agents.
As employed herein, the term “chemical warfare agent,” which is sometimes abbreviated as “CWA”, is intended to include only those agents which are effective in relatively small dosages to substantially disable or kill mammals. The term “chemical warfare agent” in this application includes substantially pure chemical compounds, but the term also contemplates mixtures of the aforesaid agents in any proportions, as well as those agents in impure states in which the other components in the mixture are not simply other CWA's. “Chemical warfare agents,” as used herein, also includes partially or completely degraded CWA's, e.g., the gelled, polymerized, or otherwise partially or totally decomposed chemical warfare agents commonly found to be present in old munitions.
In view of the advantages of rapidly and accurately identifying the presence of CW OP agents and associated by-products, and further in view of the need to address the shortcomings associated with currently available detection methods, there is still a need for new and improved detection methods and kits. The present invention addresses these needs.